Avalanche Forecast

Issued: Feb 3rd, 2012 10:34AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Cornices, Deep Persistent Slabs, Wind Slabs and Storm Slabs.

jlammers, Avalanche Canada

South Rockies.

This is the first significant warm spell of the season and the snowpack is revealing its secrets, especially in alpine locations. Make conservative terrain choices as destructive avalanches are a real possibility.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Expect clear skies and light southerly winds for the entire forecast period. An inversion is also meant to dominate the region with alpine temperatures sitting at about 1.0'.

Avalanche Summary

No new natural avalanches reported today. In the neighboring Lizard range numerous deep releases were reported on facets that formed in October. The same snowpack structure exists in many parts of the South Rockies region. This combined with the current warming at upper elevations means that you can expect an increase in avalanche activity this weekend.

Snowpack Summary

Strong SW winds have created stiff, yet reactive wind slabs on lee slopes. Cross-loading, and wind slabs are also found lower on the slopes and in unsuspecting terrain due to the strong push of the winds. Below 1700m a 4cm thick crust exists, I suspect it's from the rising freezing levels, and precipitation last Sunday. This crust is said to be supportive. Below this reports indicate the mid-pack to be fairly well settled. Deeper in the snowpack sits the mid-December surface hoar layer. This layer remains a concern for deeper releases. Basal facets and depth hoar also play a major role in this region. The big story for the weekend is warming at higher elevations due to an inversion. Cornices, and sun-exposed slopes will be a concern as will the possibility of stimulating deeper releases. In Elk Valley North and the Crowsnest, the average snowpack depth at treeline is 150 cms. Elk Valley S and the Flathead the snowpack depth is closer to 2 m.

Problems

Cornices

Cornices are large, unsupported and tender right now. Give cornices a wide berth from above and below. They usually require more space then initially anticipated. With current warming, cornices will become weak.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

3 - 6

Deep Persistent Slabs

Deep persistent slabs may be triggered with a larger trigger (cornice, sled). They may also be triggered by solar warming

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Wind Slabs

Strong SW winds have formed wind slabs on lee slopes and below ridgecrests.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Storm Slabs

Dense new storm snow has created storm slabs. These seem to be settling out and bonding, I'd be suspect of steeper features and convex rolls; especially at upper elevations

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Feb 4th, 2012 3:00AM